设置缓冲：
#define _IOFBF 0 /* Fully buffered. */ #define _IOLBF 1 /* Line buffered. */ #define _IONBF 2 /* No buffering. */ void setbuf (FILE *__restrict __stream, char *__restrict __buf); int setvbuf (FILE *__restrict __stream, char *__restrict __buf, int __modes, size_t __n);
流和文件描述符：
FILE *fdopen (int __fd, const char *__modes); int fileno (FILE *__stream);
内存流：
FILE *fmemopen (void *__s, size_t __len, const char *__modes);
原文：http://www.cnblogs.com/mfmans/p/6885406.html